[0001] The present invention relates to an enantioselective hydrogenation catalyst having
a solubility in water and more particularly to a complex of a transition metal such
as ruthenium, rhodium, iridium or palladium, and a water-soluble phosphine compound.
In another aspect, the present invention further relates to a method of enantioselectively
hydrogenating an olefin, a ketone or an imine using a catalyst having solubility in
water.
[0002] Hitherto, many reports have been reported about transition metal complexes utilizable
for organic synthesis reactions, for example, about catalysts being used for enantioselective
synthesis reactions such as an enantioselective hydrogenation reaction, an enantioselective
isomerization reaction or an enantioselective silylation reaction. In these complexes,
many of the complexes obtained by coordinating an optically active tertiary phosphine
compound to transition metals such as rhodium, palladium, ruthenium, iridium or nickel,
have an excellent performance as a catalyst for an enantioselective synthesis reaction
and for further increasing the performance of the catalysts, many phosphine compounds
having specific structures have been developed as described, e.g., in
Kagaku Sosetu (The. Elements of Chemistry) 32, "Yuki Kinzoku Sakutai no Kagaku (Chemistry
of Organometallic Complexes", 237-238(1982), edited by The Chemical Society of Japan.
[0003] In particular, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter referred
to as "BINAP") is one of excellent ligands and a rhodium complex using BINAP as the
ligand (JP-A-55-61937) (the term "JP-A" as used herein means an unexamined published
Japanese patent application) and a ruthenium complex using BINAP as the ligand (JP-A-61-6390
= EP-A-0174057) have already been reported. Also, it has also been reported that a
rhodium complex using 2,2'-bis[di(p-tolyl)phosphino]-1,1'-binaphthyl (hereinafter
referred to as "p-T-BINAP") as the ligand (JP-A-60-199898 = EP-A-0156607) and a ruthenium
complex using p-T-BINAP as the ligand (JP-A-61-63690) give good results in an enantioselective
hydrogenation reaction and an enantioselective isomerization reaction.
[0004] Furthermore, it has been reported that in an enantioselective hydrogenation reaction
of nerol using as a catalyst a rhodium complex using 2,2'-bis(dicyclohexylphosphino)-1,1'-binaphthyl
(hereinafter referred to as "CyBINAP"), citronellol having an optical purity of 66%ee
was obtained [S. Inoue, et al.,
Chemistry Letters, 1007-1008(1985)].
[0005] As described above, for providing complexes having a higher performance as a catalyst
for an enantioselective synthesis reaction, many specific phosphine compounds have
been developed but according to the reactions and the substrates being used, these
phosphine compounds are sometimes not yet sufficiently satisfactory as to separation
of the catalyst from the product formed and the reuse of the catalyst, and hence it
has been desired to develop a complex which can be easily separated from the product
formed as compared with conventional complexes (or catalysts).
[0006] As the result of the various investigations on many phosphine compounds for solving
the foregoing problem, the inventors have discovered that a transition metal complex
using as the ligand a novel phosphine compound having an alkali metal 5,5'-sulfonate
binaphthyl group in place of the binaphthyl group of BINAP has a solubility in water,
can be easily separated from the product formed, and enables the reuse of the catalyst,
and have succeeded in accomplishing the present invention based on the discovery.
[0007] According to the present invention, there is provided a novel transition metal complex
using as the ligand a dialkali metal 2, 2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate
( hereinafter referred to as " SO₃A-BINAP") represented by formula (II)

wherein A represents an alkali metal atom such as Na, K, etc.
[0008] That is, the present invention relates to an alkali metal sulfonate-substituted binaphthyl-phosphine
transition metal complex represented by formula (I)
[M(X)
n(Q)(SO₃A-BINAP)]Y (I)
wherein M represents a transition metal atom;
SO₃A-BINAP represents a tertiary phosphine represented by formula (II)

in which A represents an alkali metal atom;
X represents a chlorine atom, a bromine atom or an iodine atom;
when
n is 1, M represents ruthenium, Q represents benzene or p-cymene, and Y represents
a chlorine atom, a bromine atom or an iodine atom;
when
n is 0 and M is iridium or rhodium, Q represents 1,5-cyclo-octadiene or norbornadiene,
and Y represents Cl0₄, PF₆ or BF₄; and
when
n is 0 and M is palladium, Q represents π-allyl, and Y represents Cl0₄, PF₆ or BF₄.
[0009] The present invention further relates to a method of enantioselectively hydrogenating
an olefin, a ketone or an imine, which comprises carrying out the enantioselective
hydrogenation using as a catalyst the alkali metal sulfonate-substituted binaphthylphosphine
transition metal complex represented by formula (I) described above.
[0010] The SO₃A-BINAP which is a component of the complex can be an optically active isomer,
such as the (+)-isomer or the (-)-isomer.
[0011] The SO₃A-BINAP forms a complex with a transition metal as the ligand. A suitable
transition metal is rhodium, iridium, palladium or ruthenium.
[0012] Specific examples of the complex of the present invention are set forth below, in
which COD means 1,5-cyclooctadiene, NBD means norbonadiene, and η³-C₃H₅ means a π-allyl
group. (These abbreviation apply to the following description.)
[Rh(COD)(SO₃A-BINAP)]ClO₄
[Rh(NBD)(SO₃A-BINAP)]ClO₄
[Rh(COD)( SO₃A-BINAP)]BF₄
[Rh(NBD)(SO₃A-BINAP)]BF₄
[Rh(COD)(SO₃A-BINAP)]PF₆
[Rh(NBD)(SO₃A-BINAP)]PF₆
[Ir(COD)(SO₃A-BINAP)]ClO₄
[Ir(COD)(SO₃A-BINAP)]BF₄
[Ir(COD)(SO₃A-BINAP)]PF₆
[Ir(NBD)(SO₃A-BINAP)]ClO₄
[Ir(NBD)(SO₃A-BINAP)]BF₄
[Ir(NBD)(SO₃A-BINAP)]PF₆
[Pd(η³-C₃H₅)(SO₃A-BINAP)]ClO₄
[Pd(η₃-C₃H₅)(SO₃A-BINAP)]BF₄
[Pd(η³-C₃H₅)(SO₃A-BINAP)]PF₆
[RuI(p-Cymene)(SO₃A-BINAP)]I
[RuBr(p-Cymene)(SO₃A-BINAP)]Br
[RuCl(p-Cymene)(SO₃A-BINAP)]Cl
[RuI(C₆H₆)(SO₃A-BINAP)]I
[RuBr(C₆H₆)(SO₃A-BINAP)]Br
[RuCl(C₆H₆)(SO₃A-BINAP)]Cl
[0013] As a method of producing the transition metal complex of the present invention, there
is the same method as the synthesis method of [Rh(COD)(dppe)]ClO₄ [wherein dppe means
1,2-bis(diphenylphosphino)ethane] reported, e.g., in J.A. Osborn et al.,
Journal of American Chemical Society,
93, 2397(1971). That is, after reacting [Rh(COD)₂]ClO₄ as a raw material and SO₃A-BINAP
in a solvent such as methanol, ethanol or water, singly or in a mixture of these solvents
at room temperature from 30 minutes to overnight, by distilling off the solvent(s)
under a reduced pressure, [Rh(COD)(SO₃A-BINAP)]ClO₄ can be quantitatively synthesized.
[0014] Also, as the synthesis method of [Ir(COD)(dppe)]BF₄ reported in M. Green et al.,
Journal of Chemical Society, (A), 2334(1971), after reacting [Ir(COD)(CH₃CN)₂]BF₄ as a raw material and SO₃A-BINAP
in a solvent such as methanol, ethanol or water, singly or in a mixture of these solvents
at room temperature from 30 minutes to overnight, by distilling off the solvent(s)
under a reduced pressure, [Ir(COD)(SO₃A-BINAP)]BF₄ can be quantitatively synthesized.
[0015] Furthermore, as the synthesis method of [Pd(η³-C₃H₅)(dppe)]ClO₄ reported in Ootuka
et al.,
Chemistry Letter, 157 (1986), by reacting [Pd(η₃C₃H₅)Cl]₂ as a raw material and SO₃A-BINAP in a mixture
solvent of water and methanol in the presence of NaClO₄, [Pd(η³-C₃H₅)(SO₃A-BINAP)]ClO₄
can be synthesized.
[0016] Moreover, as the synthesis method of [RuI(p-Cymene) (BINAP)]I reported in Takaya
et al.,
Journal of Chemical Society, Chemical Communication, 609(1991), after reacting [RuI₂(p-Cymene)]₂ as a raw material and SO₃A-BINAP in
methanol solvent at room temperature from 30 minutes to overnight, by distilling off
the solvent under a reduced pressure, [RuI(p-Cymene) (SO₃A-BINAP)]I can be quantitatively
analyzed.
[0017] When the transition metal complex thus obtained is used as a catalyst for an enantioselective
synthesis reaction such as, for example, the enantioselective hydrogenation reaction
of an olefin, a ketone or an imine, the reaction can be carried out in an aqueous
solution: or the reaction is carried out in an ordinary organic solvent and after
transferring the catalyst into an aqueous layer, the catalyst can be easily separated
from the hydrogenation product.
[0018] Also, when one of the (+)-isomer and (-)-isomer of SO₃A-BINAP in the present invention
is selected and the transition metal complex using it as the ligand is used as a catalyst,
the desired product of the absolute configuration can be obtained in an enantioselective
synthesis reaction.
[0019] The following examples are intended to illustrate in more detail but not to limit
the invention .
[0020] The measurements in the examples were carried out using the following instruments.
- NMR:
- AM-400 Type Apparatus (400 MHz)
(manufactured by Bruker Inc.)
Internal standard substance:
¹H-NMR ... tetramethylsilane
External standard substance:
³¹P-NMR ... 85% phosphoric acid
- Optical Rotation:
- DIP-4 Type Apparatus (manufactured by JASCO Inc.)
- Optical Purity:
- High-Performance Liquid Chromatography L-6000
(manufactured by Hitachi, Ltd.)
Detector: UV Detector L-4000UV (manufactured by Hitachi, Ltd.)
- Chemical Purity:
- High-Performance Liquid Chromatography L-6000
(manufactured by Hitachi, Ltd.)
Detector: UV Detector L-4000UV
(manufactured by Hitachi, Ltd.)
- Elemental Analysis:
- CHN 2400 (manufactured by Perkin-Elmer Co.)
- Chemical Purity:
- Gas Chromatography
(manufactured by Hewlett Packard Ltd.)
Column: HP-1 0.25 mmφ x 25 m
- Chemical Purity:
- Gas Chromatography GC-9A
(manufactured by Shimazu Corporation)
Column: PEG-HT 0.25 mmφ x 25 m
EXAMPLE 1
Synthesis of sodium (+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate
[(+)-SO₃Na-BINAP]:
[0021] To 20 ml of 95% H₂SO₄ was slowly added dropwise 40 ml of 30% SO₃-H₂SO₄.
[0022] To the solution was added 10 g (16 mmols) of (+)-BINAP, the temperature of the mixture
was gradually raised to 40°C with stirring, and the mixture was further stirred for
2 hours at the same temperature. Then, the reaction mixture obtained was added dropwise
to an aqueous NaOH solution (94 g of NaOH and 360 ml of water) under water cooling.
Precipitates thus formed were recovered by filtration, washed with water, and dried
under a reduced pressure. To the solids obtained were added 2 liters of ethanol followed
by refluxing for one hour by heating, thereafter, insoluble matters were filtered
off, and the filtrate was concentrated to dryness. The solids obtained were recrystallized
from 200 ml of ethanol to provide 4.88 g of sodium (+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate.
The percent yield thereof was 37%.
[0023] Melting point > 300°C.
[0024] ¹H-NMR (CD₃OD) δ:
6.76-7.26 (m, 24H), 7.47-7.50 (m, 2H), 7.98-8.00 (m, 2H), 8.92-8.94 (m, 2H)
[0025] ³¹P-NMR (CD₃OD) δ: -15.8 (S)
[0026] [α]
D²⁵ = +3.06° (C 0.45 CH₃OH)
[0027] Elemental Analysis for C₄₄H₃₀O₆S₂Na₂(H₂O)₅:
- Calculated:
- C 57.64 H 4.40
- Found:
- C 58. 05 H 4.13
EXAMPLE 2
[0028] In a 50 milli-liter flask with side arm were placed 0.1023 g (1.05 x 10⁻⁴ mol) of
[RuI₂(p-Cymene)₂]
n synthesized by the method described in Mashima et al.,
Journal of Chemical Society, Chem. Commun., 1208(1989) and 0.2001g (2.42 x 10⁻⁴ mol) of (+)-SO₃Na-BINAP obtained in Example
1 and after displacing the atmosphere in the flask with a nitrogen gas, 5 ml of methanol
was added to the mixture followed by stirring for 15 hours at room temperature. After
filtering off insoluble matters with celite filter aid, methanol was distilled off
from the filtrate and the residue formed was dried under a reduced pressure to provide
0.29 g of iodo-π-p-Cymene[sodium 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate]ruthenium
iodide[RuI(p-Cymene)((+)-SO₃Na-BINAP)]I. The yield was quantitative.
[0029] ³¹P-NMR (CD₃OD) δ:
25.15 (d,J = 59.74 Hz), 40.71 (d,J = 59.35 Hz)
[0030] Elemental Analysis for C₅₄H₄₄O₆S₂P₂Na₂I₂Ru:
- Calculated:
- C 49.30 H 3.37
- Found:
- C 48.74 H 3.51
Solubility in Water: 0.8% by weight.
EXAMPLE 3
[0031] In a 50 milli-liter flask with side arm were placed 0.28 g (5.97 x 10⁻⁴ mol) of [Ir(COD)(CH₃CN)₂]BF₄
synthesized by the method described in M. Green et al.,
Journal of Chemical Society, (A), 2334(1971) and 0.50 g (6.05 x 10⁻⁴ mol) of (+)-SO₃Na-BINAP obtained in Example
1 and after displacing the atmosphere in the flask with a nitrogen gas, 10 ml of methanol
and 5 ml of water were added to the mixture followed by stirring for 15 hours at room
temperature. After filtering off insoluble matters with celite, the solvents were
distilled off from the filtrate and the residue was dried at a reduced pressure to
provide 0.76 g of 1,5-cyclooctadiene-[sodium 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate]iridium
tetrafluoroborate[Ir(COD)((+)-SO₃Na-BINAP)]BF₄. The yield was quantitative.
[0032] ³¹P-NMR(CD₃OD) δ: 16.04 (S)
[0033] Elemental Analysis for C₅₂H₄₂O₆S₂P₂Na₂BF₄Ir(H₂O)₅:
- Calculated:
- C 47.89 H 4.02
- Found:
- C 48.13 H 3.9 6
[0034] Solubility in water: 0.1% by weight.
EXAMPLE 4
[0035] In a 50 milli-liter flask with side arm were placed 0.21 g (5.51 x 10⁻⁴ mol) of [Rh(C₇H₈)₂]ClO₄
synthesized by the method described in T.G.Schenck et al.,
Inorganic Chemistry, 2334(1985) and 0.50 g (6.05 x 10⁻⁴ mol) of (+)-SO₃Na-BINAP obtained in Example 1
and after displacing the atmosphere in the flask with a nitrogen gas, 10 ml of methanol
and 3 ml of water were added to the mixture followed by stirring for 15 hours. Then,
after filtering off insoluble matters with celite, the solvents were distilled off
from the filtrate and the residue was dried at a reduced pressure to provide 0.57
g of bicyclo[2,2,1]hepta-2,5-diene-[sodium 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-5,5'-disulfonate]rhodium
perchlorate [Rh(C₇H₈)((+)-SO₃Na-BINAP)]ClO₄. The percent yield was 93%.
[0036] ³¹P-NMR(CD₃OD) δ: 26.29 (d,J = 78.04 Hz)
[0037] Elemental Analysis for C₅₁H₃₈O₁₀S₂P₂Na₂ClRh(H₂O)₇:
- Calculated:
- C 49.08 H 4.20
- Found:
- C 48.75 H 4.03
[0038] Solubility in Water: 0.4% by weight
APPLICATION EXAMPLE 1
Enantioselective Hydrogenation Reaction of Ethyl Acetoacetate:
[0039] Under a nitrogen gas atmosphere, 0.0096 g (7.3 x 10⁻⁶ mol) of [RuI(p-Cymene)((+)-SO₃Na-BINAP)]I,
0.1164 g (7.8 x 10⁻⁴ mol) of NaI, 1 ml (7.5 x 10⁻³ mol) of ethyl acetoacetate, and
1.5 ml of water were charged in a 100 milli-liter autoclave. After displacing the
inside atmosphere of the autoclave with a hydrogen gas, the autoclave was pressurized
at a hydrogen pressure of 50 kg/cm² and the mixture was stirred for 40 hours at 65°C.
After the reaction was over, the hydrogen gas was removed, and after added thereto
100 ml of water and 100 ml of ether, the ether extraction was carried out. The ether
extract was recovered, dried with anhydrous sodium sulfate, and further ether was
distilled off to provide 0.62 g (percent yield 63%) of ethyl 3-hydroxybutyrate. By
analysis by gas chromatography (PEG-HT), the conversion ratio was determined to be
99%.
[0040] Also, to a mixture of 0.0542 g (4.81 x 10⁻⁴ mol), 0.10 g (4.27 x 10⁻⁴ mol) of (R)-(+)-α-methoxy-α-trifluoromethylphenyl-acetic
acid (MTPA), 0.0891 g (4.31 x 10⁻⁴ mol) of N,N′-dicyclo-hexylcarbodiimide, and a small
amount of 4-dimethylaminopyridine was added 5 ml of methylene chloride, after stirring
the mixture for 3 hours at room temperature, the solvent was distilled off. Then,
5 ml of ether was added to the solid residue formed and the dissolved portion was
recovered to provide the MTPA ester of ethyl (-)-3-hydroxybutyrate.
[0041] By a diastereomer ratio analysis with gas chromatography (PEG-HT), the optical yield
of ethyl (-)-3-hydroxybutyrate was determined to be 91%ee.
[0042] Also, after the reaction was over, the reaction mixture was extracted twice with
200 ml of toluene under a nitrogen gas stream, after recovering ethyl 3-hydroxybutyrate
as the product, 1 ml of ethyl acetoacetate was added again to the aqueous layer and
the hydrogenation was carried out under the same condition as above, thereby the same
result as above could be obtained. Thus, it can be seen that the complex of this invention
can be utilized as an excellent catalyst which can be repeatedly used.
APPLICATION EXAMPLE 2
Enantioselective Hydrogenation Reaction of Acetophenonebenzylimine:
[0043]
(1) Under a nitrogen gas atmosphere, to a mixture of 0.014 g (2.1 x 10⁻⁵ mol) of [Ir(COD)Cl]₂
and 0.036 g (4.4 x 10⁻⁵ mol) of (+)-SO₃Na-BIAP was added 3 ml of methanol and the
resultant mixture was stirred for one hour at room temperature to obtain a mixture
Ir(COD)((+)-SO₃Na-BINAP)Cl.
(2) Under a nitrogen gas atmosphere, the mixture obtained in above step (1, 0.91 g
(4.4 x 10⁻³ mol) of acetophenonebenzylimine, and 2 ml of methanol were charged in
a 100 milli-liter autoclave. After displacing the inside atmosphere of the autoclave
with a hydrogen gas, the autoclave was pressed at a hydrogen pressure of 50 kg/cm²
and the mixture was stirred for 12 hours at room temperature. After the reaction was
over, the hydrogen gas was removed and after distilling off methanol from the reaction
mixture, 100 ml of an aqueous sodium hydroxide solution of I mol concentration and
100 ml of ether were added to the residue to carry out the extraction of the product
formed into the ether layer. After separating the organic layer (ether layer) from
the aqueous layer, the organic layer was dried with anhydrous sodium sulfate and then
the solvent was distilled off to provide 0.64 g (percent yield 70% of N-benzyl-α-phenethylamine.
[0044] By a gas chromatographic analysis, the conversion ratio was determined to be 99%and
the selectivity was 90%.
[0045] Also, after distilling the product, the optical rotation was measured and in this
case, [α]
D²⁵ was -22.78° (C = 1.17 ethanol).

APPLICATION EXAMPLE 3
[0046] Enantioselective Hydrogenation Reaction of Aminomethyl Phenyl Ketone:

[0047] Under a nitrogen gas atmosphere, 0.20 g (1.2 x 10⁻³ mol) of aminomethyl phenyl ketone
hydrochloride, 0.0042 g (3.9 x 10⁻⁶ mol) of a catalyst, Rh(COD)((+)-SO₃Na-BINAP)Cl
formed by mixing [Rh(COD)Cl]₂ and (+)-SO₃Na-BINAP, and 5 ml of water were charged
in a 100 milli-liter autoclave. After displacing the inside atmosphere of the autoclave
with hydrogen gas, the autoclave was pressurized at a hydrogen pressure of 30 kg/cm²
and the mixture was stirred for 64 hours at room temperature. After the reaction was
over, the hydrogen gas was removed, precipitates formed were filtered, and 100 ml
of an aqueous sodium hydroxide solution of 1 mol concentration and 100 ml of ether
were added to the filtrate to extract the product into the ether layer. After separating
the organic layer (ether layer) from the aqueous layer, the organic layer was dried
with anhydrous sodium sulfate and then the solvent was distilled off to provide 0.09
g of a mixture of 2-amino-1-phenyl ethanol and 2-amino-1-cyclohexyl ethanol.
[0048] By analyzing the reaction mixture obtained with high-performance liquid chromatography
and gas chromatography, it was confirmed that the conversion ratio was 18% and the
ratio of 2-amino-1-phenyl ethanol to 2-amino-1-cyclohexyl ethanol was 1 : 1.
[0049] The mixture was separated and purified by a silica gel column (chloroform/methanol
= 5/1) and the optical rotation of 2-amino-1-phenyl ethanol was measured.
[0050] In this case, [α]
D²⁵ was +8.54° (C = 0.11, ethanol).
[0051] HPLC Condition:
Column: Cosmosil 5Ph (trade name, manufactured by Nacalai Tesque, Inc., 4.6 mm
x 250 mm)
Transfer Phase: 0.05M NaH₂PO₄ (pH 2.4)
Flow Rate: 1.0 ml/min.
Wavelength: 210 nm
[0052] As described above, the water-soluble alkali metal sulfonate-substituted binaphthylphosphine
compounds of the present invention form complexes with a transition metal such as
rhodium, ruthenium, iridium or palladian, and the complexes can be used as very important
catalysts for various enantioselective synthesis reactions. Thus, the foregoing compounds
of the present invention have high industrially utilizable values.